This invention relates to an improvement in the manufacture of friction clutches of the type employed in automotive vehicles, and more particularly to a clutch exhibiting generally constant actuating pressure.
In the prior art, clutches for vehicles were constructed such that an increasing force was required as the clutch pedal was depressed to actuate the clutch. The constantly changing force tended to make it difficult to smoothly operate the clutch and tiring to hold the clutch pedal down with the clutch in the disengaged position.
For example, U.S. Pat. No. 2,037,610 discloses a disk clutch in which a ring linked to a clutch pedal engages the inner ends of a plurality of radially extending levers having outer ends which are hingedly connected to a pressure ring of a clutch. The levers are pivoted intermediate the ends on a clutch encasing cover such that a longer lever arm is defined between the pivot point and the inner end of the lever and a shorter lever arm is defined between the pivot point and the outer end of the lever. As the clutch pedal is depressed, the force required to move the pressure ring to compress pressure springs increases.
U.S. Pat. No. 4,502,959 and U.S. Pat. No. 4,601,277 disclose a clutch of the type presently commercially available for use in vehicles. A plurality of clutch levers have inner ends which are engaged by a throw-out bearing and have outer ends which engage a pressure plate. The levers are pivotally connected to a clutch cover at points adjacent the outer ends. Intermediate the inner end and the pivot point there is formed a nose on each lever which nose engages a collector ring which in turn engages a Belleville spring to maintain the clutch in the engaged position. When the clutch pedal is depressed to disengage the clutch, the throw-out bearing is moved against the inner ends of the levers which pivot on the cover rotating the outer ends of the levers away from the pressure plate. At the same time, the noses move the collector ring to collapse the Belleville spring thereby releasing the axial pressure against the pressure plate. As in the previously described prior art clutch, a longer lever arm is defined between the pivot point and the inner end of the lever body and a shorter lever arm is defined between the pivot point and the nose. Thus, the force required to depress the clutch will increase with travel as the levers attempt to collapse the Belleville spring.